Electromagnets



Nov. 12 1957 A. E. LILLQUKST ELECTROMAGNETS Filed April 16. 1954 ZQFWEDWE United States Patent ELECTROMAGNETS Arvid E. Lillqnist, Wauwatosa, Hammer, Inc., Milwaukee, ware Wis., assignor to Cutler- Wis., a corporation of Dela- This invention relates to improvements in electromagnets, and more particularly to improvements in the structural features of electromagnets used for lifting and the like.

In the construction of lifting magnets it has long been a problem to reduce their size and weight without reducing their lifting capacity or impairing their ability to withstand abuse. More recently the problem of reducing the current requirements has been brought into prominence by the adoption of new applications for lifting magnets. For example, where magnets are to be used on fork lift trucks with battery power, minimizing the amount of current drain is a vital feature.

Accordingly an object of the invention is to provide an improved electromagnet construction which for a given lifting capacity is smaller and lighter than electromagnets as heretofore proposed.

Another object of the invention is to effect a radical reduction in the current requirements of lifting magnets.

A further object of the invention is to provide an electromagnet having the aforementioned desirable character- 3 flame 10 is adapted to ly mOd t istics while eliminating the necessity for the usual steel castings and the patterns required for producing the same.

Other objects and advantages of the invention will hereinafter appear.

Heretofore, because of the extremely rough usage encountered by lifting magnets it has been the practice to make the several parts thereof out of relatively heavy metal castings. My invention contemplates a reduction in the number of said parts and the fabrication of said parts out of readily available stock materials, such as metal plate, bar stock and tube stock. Although I will herein show and describe my invention in an embodiment which is especially adapted for use with fork lift trucks where the fork is used to pick up the magnet and the magnet is then used to or other magnetic material to be transported, it is to be understood that the invention is likewise applicable to magnets intended for other uses.

Inthe drawings, Figure l is a view in section on the line 1-1 of Fig. 2 illustrating the structural details of my improved electromagnet, and

Fig. 2 is a bottom plan view, on a reduced scale, of the electromagnet illustrated in Fig. 1.

In Figs. 1 and 2 of the drawings the numeral 10 designates the magnet frame, which is shown as machined from the required length of low cost readily obtainable (preferably round) bar stock of a suitable diameter, as indicated at the circular upper end portion 11 thereof. Said upper end portion is machined to provide a relatively large and relatively deep, preferably concentric, circular recess 12, which is utilized to provide a terminal box for wiring of the magnet.

As shown in Fig. 1, and in dotted lines in Fig. 2, an insulating block 13 is attached by screws 14, 14 to the bottom wall 12* of recess 12. Although block 13'is shown as of the four terminal type, only two of the four terminal plates 15 are required to respectively electrically connect outer diameter of the insulated terminal wires 16 and 17 of the magnet winding with the insulated terminal wires 18 and 19 from a suitable source of energy supply, such as a battery. A suitable opening 20 is drilled through the peripheral wall of recess 12 to provide for insertion of the terminal wires 16 and 17 of the magnet winding.

A second opening 21 is drilled through the peripheral wall of recess 12; the inner end of said openingbeing of a size to provide clearance for the rubber covering 22 surrounding the aforementioned terminal wires 18 and 19. The outer end portion 21*- of opening 21 is of greater diameter; the same being tapped to accommodate a suitable packing gland 23 having an opening therethrough to accommodate with a rather close fit the aforementioned rubber covering 22. Prior to insertion of gland 23 a suitable amount of waterproof packing 21 is forced into the space between the covering 22 and portion 21 of opening 21, so that upon inward driving of gland 23 in a well known manner said packing is caused to tightly grip the rubber covering 22 and the inner end of portion 21 of said opening, thus providing a watertight connection between said parts.

The magnet frame 10 has its lower end portion machined to provide a concentric circular cavity or recess 24. The aforementioned length of round bar stock from which frame 10 is fabricated is peripherally cut away as indicated at 25 to provide the downwardly facing horizontal annular shoulder 26. The periphery of said length of round bar stock is further cut away to slightly reduce the the lower end portion of frame 10, as indicated at 27 in Fig. 1. The vertical length of the cut away portion 25 preferably corresponds substantially exactly with the thickness of the top plate 28 of the magnet, whereas the balance of the downward length of the annular magnet coil or winding 29. Frame 10 is additionally peripherally cut away from a point adjacent its lower end as indicated at 30, and a peripheral groove 30 is formed in cut away portion 30, preferably after frame 10, top plate 28 and outer pole member33 have been united, for purposes hereinafter described.

The machining of frame 10 as aforedescribed provides an annular inner pole face 31 of preselected dimensions with respect to the dimensions of the outer pole face 32 of the outer pole member 33, which will now be described.

' 33 are assembled with respect to each other.

, which is adapted to have a rather close spending vertical shoulder 34 formed on said pole mem- Said outer pole member 33 is initially cut to the required length from standard commercial pipe of the desired inner and outer diameters. The inner periphery of the upper m end of said length of pipe is annularly machined or otherpick up a magnetic metal plate wise cut away to provide a pair of right-angled shoulder portions 34, and the top plate 28 of the magnet is provided with a downwardly facing circular groove 35 of rectangular form in cross section the inner periphery of fit with the correber 33. Alternatively said outer pole member 33 could readily be fabricated by rolling a cylinder from a bar or plate of proper thickness and joining the ends thereof by welding.

The lower end of outer pole member 33 is preferably machined to provide the upwardly and inwardly extending beveled surface 36, and the inner diameter of member 33 is likewise increased by machining adjacent the beveled surface 36, as indicated at 37. The upper end of the cut away portion 37 is alined with the upper end of the cut away portion 30 of the inner pole 31 of the magnet. Also formed in the surface of cut away portion 37 of outer pole member 33 is a groove 37, which is alined with the aforementioned groove 30 in the frame member 10 when the magnet frame 10, top plate 28 and outer pole membe Top plate 28 and magnet frame 10 are preferably assembledzandri idly andpermanently united in the relative posit on hereofillustr teclinFigs. 1 and2. For example, the top plate 28 may be seated upon a support of suitable form (not shown), and the-lower end of magnet frame .0 n in er ed: ownwardly withaarather. close fit through the circularopening 28 gprovidedinztop .plate 28, until the annular shoultlfililfi onzsaidframeseats .against the polenremberfi} is :rigidly ;held in engagement with top plate .28isaid partsare rigidly and permanently united by a sealed connection represented --by the continuous weld .40 around the adjacent portions of ,outer pole member 33 and topplate28.

With frame 10,.topplate 28 and outer pole member 33 so united, and positioned as last mentioned, the magnet coil 29 .may be insterted into the annular recess afforded by said parts;.care.being taken to insure that the terminal wires16, and 17-of themagnet coil .29 are alined with and inserted through the opening into terminal recess 12. Prior tOinsertion vofmagnet coil 29 I prefer to first slide overthe magnet-frame) a slotted washer 39 (Fig. 1) of suitable insulating material. The slot 39 (Fig. 1) in said washer is alined with said opening 20 leading to terminal recess 12; saidslot accommodating the insulated terminal wires.16.'and.,17 ofcoil29, as shown.

While theaforementioned assembled parts are allowed to remainzin inverted position, the space around coil 29 is filled with a suitable impregnating compound 41 in moltenordiquid condition, upto or substantially in line withthe horizontal-annularshoulder 37 (Fig. 1). There after .the annular non-magnetic metal coil shield 42 is placed ,inposition, as shown, in contact with the fill of impregnating material 41. If necessary or required to effect proper tight clamping of coil 29 in position by the annular metal plate 42 forming the coil shield when the latter, is .properly positioned and secured, and annular insulating spacing .washer tnot shown) may be interposed between coil shield ;42 .and the-fill of impregnating compound 41.

With coil shield 42.pressed into the desired position, as shown, in -any.suitable or desired manner, the same is calked, as indicated at 43; and .43 in Fig. l, by use of theereguired-qlengths ofstring babbitt of suitable gauge (such as No. 7 Brown & Sharpe).

.Priorto closureand sealing of the open upperend of wiring terminal recess .12 .(Fig. l) the terminal wires 16 and 17 of the magnet coil 29 are respectively attached by suitable binding screws or the like to two of the wiring terminal plates 15 (Fig. 2).and the lead wires 18 and 19 are likewise attached to saidterminalplates respectively; the rubber covered lead-in conductor 22 containing wires 18 and 19 being provided with a water-tight seal or connection in hole 21, 219 ,by the aforementioned packing material ,21 and thescrew-threaded stufiing gland 23. Thereuponthe gasket 4.4.of rubber or similar waterproof material and metal coverplate 45 are poistioned as shown over the open upper. end of recess 12 and secured thereto byasuitablenumberof clamping bolts, two of which are shown at 46; theithreaded shanks of bolts 46 penetrating alinefd openings in.plate .45 and gasket :44 and taking into tapped recesses (not shown)--in,the upper end portion 11 of magnet frame 1.0.

.In the mannenafqtfidficribed all parts of the magnet coil 29 and e elements therefor1are effectively sealed against the entrance of moisture or liquids of any kind. As .aforestated the conductor 22 is of sufiicient length to connect with a suitable source of energy, such as a battery upon a forked lift truck or the like.

When used as a lift truck mounted magnet the top plate 28 is provided with two pairs of arms or extensions 28 28 and 28, 28 said top plate 28 having rigidly attached to the lower face thereof two pairs of downwardly projecting rectangular metal studs 28 28 and 28 28 each of said studs being shown as fillet welded, along at least two sides thereof, to its associated arm or extension of plate 28 (see Fig. 2). a

When a magnet like that herein illustrated is used with a forklift-type truck, the same is inserted between the two spaced projections of. thetruck fork, so that the bottom surfaces of the pairs of projections 28*, 28 and 28, 28

overlie the respective prongs of the fork; the respective pairs of studs 28, 28 and 28 28 being positioned betweentheinner edges'of the fork prongs. The fork lift truck may beprovided with any suitable known means to :prevent endwise sliding movement of the magnet relatively to the fork.

Assuming that the-outer pole of a magnet likezthat herein disclosed has an outside diameter of twelve inches the weight of the complete device illustrated would be ninety pounds, and the ratedlifting capacity of the magnet.(for lifting-dock Plates, for example) would be as follows, for hal tim d y In practice I prefer to fabricate the magnet frame 10 fromtherequired length of hot rolled low carbon steel of round cross-section as aforementioned. The outer pole 33. of. themagnet is preferably machined from a section of the required length of cold drawn seamless low carbon steel tubing. The top plate 28 is preferably formed in any suitable manner from a plate of hot rolled low carbon steehandthe metal cover plate 45 forthe wiring terminal recess '12 is preferably punched from a sheet of hot rolled low carbon steel.

'It will beapparent to those skilled in the art that the basic design herein disclosed may be utilized in making other sizes of relatively small magnets. It is also to be understood that a-magnetof the character herein contemplated m-ayzbe built without the supporting arms of -the top plate, or,in.such form that the magnet can becarried by lugs and chains, along-the lines of conventional forms of liftingmagnets.

As aforeindicated the magnet specifically shown and described herein was designed to lift plates of various sizes-from one-fourth inch to seven-sixteenths inch thick; it being understood that the greatest magnetic pull would be on the seven-sixteenths inch plate; it also beingunderstood that the greatest amount-of magnetic flux would be carried through the magnet into a plate of the last mentioneldthickness. If-the plate to be handled is greater than seven-sixteenthsinch thick the proportional-sizes or areas of :the inner and outer poles of the magnet may readilytbe modified or varied, using the same basic stock materials,1in orderto obtain more magnetic pull.

Alsoit will beapparent to those skilled in the art that a magnet such as thatherein disclosed may be modified or designed, using the same basic stock materials, to handle scrap or heavy plate. The only differences in sucharnodified magnet from that herein disclosed would be thatthe inner pole face of the magnet would be left solid (by not machining the magnet frame to provide theirecess 2,4);qthe charnfer 36 at the inside diameter of the outer pole face 32 would be omitted; and the thickness of the top plate (to be substituted for top plate 28) would be approximately twice as great, with a correspond ing increase in the total height of the magnet frame.

Various other modifications in the details of construction of the magnet herein disclosed may be made without departing from the spirit and scope of my invention as defined in the appended claims.

I claim:

1. In an electromagnet of relatively small size with reference to its lifting capacity, in combination, a magnet frame consisting of a preselected length of magnetic steel bar stock of suitable cross-section to provide an inner pole, said frame having a downwardly facing peripheral shoulder formed thereon intermediate the upper and lower ends thereof and a second downwardly facing shoulder of smaller cross-sectional dimensions formed thereon adjacent the lower end thereof, a wiring terminal recess formed in the upper end of said magnet frame, a fiat top plate of magnetic steel, said top plate having an opening formed therein to permit insertion and positioning of said frame with said first mentioned shoulder seated against said plate, a continuous peripheral welded and sealed connection between said top plate and said frame to permanently unite the same, an outer pole member of tubular form composed of magnetic steel, one end of said outer pole member being united with said top plate by a continuous peripheral weld, a magnet coil positioned between said frame and said outer pole member and having its terminal wires located within said terminal recess, and a coil shield of non-magnetic metal underlying said magnet coil between said outer pole member and said inner pole and having a sealed connection with each pole.

2. An electromagnet of the character defined in claim 1, wherein means are provided to afford exit of a plurality of conducting wires from said terminal recess through a sealed opening, a metal member overlying the open end of said terminal recess and removably secured thereto, and a gasket interposed between said metal member and said recess to effect sealing of the latter.

3. In an electromagnet of relatively small size with reference to its lifting capacity, in combination, a magnet frame consisting of a preselected length of low carbon steel bar stock of round cross-section to provide an inner pole, said frame having a reduced lower end a wiring terminal recess formed in the upper end thereof, said frame also having a peripheral annular shoulder formed thereon at a predetermined point in the length thereof, a fiat top plate of low carbon steel, said top plate having an opening formed therein to permit insertion of the reduced end of said frame to effect seating of said peripheral annular shoulder against one face of said plate, a continuous peripheral welded and sealed connection between said top plate and said frame to permanently unite the same, said top plate having a circular groove formed in the other face thereof, an outer pole member of cylindrical form composed of low carbon steel, one end of said outer pole member being adapted to seat within said groove, a continuous peripheral welded and sealed connection between said top plate and said outer pole member, a magnet coil positioned between said frame and said outer pole member and having its terminal wires located within said terminal recess, a coil shield of nonmagnetic material underlying said magnet coil between said outer pole member and said inner pole and having a sealed connection with each pole, and said top plate having two like pairs of arms formed integrally therewith and respectively extending from opposite sides thereof substantially beyond the periphery of said outer pole member, for the purpose set forth.

4. As an article of manufacture, a frame for an electromagnetic lifting magnet of relatively small size with respect to its lifting capacity, said frame consisting of a single piece, of desired length, of magnetic steel round bar stock, said piece having at least three portions of its length of different outside diameters, the upper end portion being of greatest diameter and providing a downwardly facing annular shoulder adapted to seat against the upper surface of a perforated sheet metal top plate for the magnet, the lower end portion being of smallest diameter and providing a downwardly facing annular shoulder, an annular non-magnetic metal coil shield the inner portion of which is adapted to seat against said shoulder, the upper end of said frame having therein an upwardly opening wiring terminal recess of substantially cylindrical contour, and means comprising a metal plate and an interposed sealing gasket secured to the upper end of said frame and overlying the open end of said recess to assist in rendering the same liquid tight.

5. As an article of manufacture, a frame for an electromagnetic lifting magnet of relatively small size with respect to its lifting capacity, said frame consisting of a single piece, of desired length, of magnetic steel round bar stock, said piece having at least three portions of its length of different outside diameters, the upper end portion being of greatest diameter and providing a downwardly facing annular shoulder adapted to seat against the upper surface of a perforated sheet metal top plate for the magnet, the lower end portion being of smallest diameter and providing a downwardly facing annular shoulder, an annular non-magnetic coil shield the inner portion of which is adapted to seat against said shoulder, the upper end of said frame having therein an upwardly opening wiring terminal recess of substantially cylindrical contour, means comprising a metal plate and an interposed sealing gasket secured to the upper end of said frame and overlying the open end of said recess to assist in rendering the same liquid tight, and the lower end of said frame having therein a downwardly opening recess of substantially cylindrical contour to provide an annular inner pole face whose total active area bears a predetermined proportionality to the thickness of said top plate.

6. As an article of manufacture, a frame for an electromagnetic lifting magnet of relatively small size with respect to its lifting capacity, said frame consisting of a single piece, of desired length, of low carbon steel round bar stock, said piece having at least three portions of its length of different outside diameters, the upper end portion being of greatest diameter and providing a downwardly facing annular shoulder adapted to seat against the upper surface of a perforated sheet metal top plate for the magnet, the lower end portion being of smallest diameter and providing a downwardly facing annular shoulder, an annular nonmagnetic metal coil shield the inner portion of which is adapted to seat against said shoulder, the upper end of said frame having therein an upwardly opening wiring terminal recess of substantially cylindrical contour, means comprising a metal plate and an interposed gasket secured to the upper end of said frame and overlying the open end of said recess to assist in rendering the same liquid tight, and the lower end of said frame having therein a downwardly opening recess of substantially cylindrical contour to provide an annular inner pole face whose total active area bears a predetermined proportionality to the thickness of said top plate.

7. In an electromagnet of relatively small size with reference to its lifting capacity, in combination, a magnet frame consisting of a preselected length of magnetic steel bar stock of round cross-section to provide an inner pole, said frame having a wiring terminal recess formed in the upper end thereof, said frame also having a peripheral shoulder formed thereon at a predetermined point in the length thereof, a top plate of magnetic steel, said top plate having an opening therein to permit insertion of one end of said frame to effect seating of said peripheral shoulder against one face of said plate, a continuous peripheral welded and sealed connection between said top plate and said frame to permanently .unite the same, said top plate having a circular groove formed therein, an outer pole member of tubular .form

tween said top plateand said outer pole member, a magnet coil positioned between said frame and said outer pole member and having its terminal wires located within said terminal recess, and a non-magnetic coil shield underlying said magnet coil between said outer pole member and said inner pole and having a sealed connection with each pole.

8. =In an electromagnet of relatively small size with reference to its lifting capacity, in combination, a magnet frame consisting of apreselected length of magnetic steel bar stock of round cross-section to provide an inner pole,'said frame having a wiring terminal recess formed in the upper end thereof, said frame also having a pc- 'ripheral shoulder formed thereon at Ya predetermined point in the length thereof, a top plate of magnetic steel, said top plate having an opening therein to permit insertion of one end of said frame to effect seating of said peripheral shoulder against one face of said plate, a continuous peripheral welded and sealed connection between said top plate and said frame to permanently unite the same, said top plate having a circular groove formed therein, an outer pole member of tubular form composed of magnetic steel, one end of said outer. pole member being adapted to seat Within said vgroove, a continuous peripheral welded and sealed ,connection between saidtop plate and said outer pole member, a magnet coil positioned between said frame .and said outer pole member and having its terminal wires located within said terminal recess, a non-magnetic coil shield underlying said magnet coil between said outer pole member and said inner pole and having a sealed connection with each pole, means affording .exit of a plurality of conducting wires from said terminal recess through a sealed opening, a metal member overlying the open endof said recess andremovably secured-thereto, and a-ga'sket interposed between said metal member and said recess to seal the latter. 7

References Cited in the file ofthis patent UNITED STATES PATENTS 710,041 Clard Sept. 30, 1902 1,147,682 Jackson July 20, 1915 1,945,383 Sauer Jan. 30, 1934 2,095,499 Hodgson' et a1. Oct. 12, 1937 FOREIGN PATENTS 185,280 Great 'Britain Sept. 7, 1922 1,043,701

France Nov. 10, 1953 

